The Big Risk: Running uphill increases the load on your calves and Achilles, says Bryan Heiderscheit, P.T., Ph.D., of the University of Wisconsin sports medicine center.

The Fix: Do calf raises: Balance on a step on your right foot so your heel hangs off it; raise your left foot behind you. Rise onto your toes; then lower your heel as far as you can. Do 2 sets of 10 to 15 reps with each leg twice a week.

2. ILIOTIBIAL BAND SYNDROMEThe Problem: The IT band is a fibrous tissue on the outside of your thigh that stabilizes your knees and hips. If your hips and knees twist too much, the IT band rubs your lateral femoral condyle, a prominent part of your thigh bone, causing pain on the outside of your knee.

The Big Risk: A long stride! increases force on your knees and IT bands.

The Fix: To shorten your stride, boost your step rate by 5 to 10 percent, Heiderscheit says. Try to avoid landing hard on your heel, and keep your knee flexed about 20 degrees. Have a friend take video of you so you can check your form.

3. SHINSPLINTSThe Problem: You feel pain and soreness because your tibialis posterior muscle is pulling away from your shin bone. This muscle works with a larger calf muscle, your soleus, says Reed Ferber, Ph.D., director of the running injury clinic at the University of Calgary. "Your tibialis posterior is overworked and has to pull more of its weight," Ferber says.

The Big Risk: Weak muscles can expose you if you're new to running or returning after a hiatus.

The Fix: Strengthen your tibialis posterior and soleus muscles with calf raises. Also try seated ankle invertors: Sit with your leg straight and loop a resistance band around your foot. Making sure your leg doesn't rotate, pull the top of your foot inward for 2 seconds, and release for 2 seconds. That's 1 rep. Do 1 set of 10 reps a day, working up to 3 sets a day.

4. PLANTAR FASCIITISThe Problem: The tight, 1 thick plantar fascia supports the arch and works with a network of muscles across the bottom and sides of your foot. You may feel a sharp pain on the bottom of your heel, especially in the morning (the tissue shortens at night).

The Big Risk: Weak I foot muscles strain the plantar fascia.

The Fix: Do towel crunches: Put a towel on the floor, your heels on the ground, and your toes on the towel. "Make fists with your toes and scrunch the towel up," Ferber says. Do this every day for 15 minutes.

The Big Risk: Running on steep or uneven terrain could cause runner's knee.

The Fix: Strengthen your hip muscles, which control your thigh bones. Try these two moves, doing 1 set of 10 reps and working up to 3 sets a day. The standing hip abductor: Stand with one foot in the loop of a resistance band and the other foot on top of the band (adjust the length to control the resistance). Move the banded leg 2 seconds out, 2 seconds in. Then work your I hip gluteus medius: Loop the band around and face a chair; move the banded leg back to 45 degrees, 2 seconds out, 2 seconds in.